I have never understood why people ever thought Favors was a beast. He only had three years of his entire career where he averaged over 8 rebounds. Ironically enough, his highest rpg (8.7) was the year after we let Millsap go. You know how many rpg Millsap averaged the season before? You got it, 8.8. Millsap has had 4 years averaging over 8 rpg. He even had one year averaging 9. You also have to consider this - Millsap was used as a ball handler in Atlanta and was taking over 3 3pt's per game. Since Favors has no range, he is actually hanging around the basket a bunch more than Millsap. And, he still didn't get as many rebounds. So no, Favors is not a better rebounder.
Favors has averaged 1.3 blocks per game in his career. Millsap has averaged 1. So I guess you got me on that one although I think it's pretty negligible.
As for rolling, well, I disagree with you there. Millsap can be the one setting the pick AND the one with the ball. He has been that versatile. So maybe Favors finishes at the rim a tad better, but I take the guy who can be on both sides of that fundamental part of the game.
Millsap has been a very good NBA player for the last decade. Favors has just been a solid player. It's too bad he never got a chance to be a starting center. That was his best role. But we should have kept Millsap. Terrible move by DL.
I don't disagree that Millsap would be a better fit and the more versatile player. I disagree with your statement that Millsap was better than Favors at everything.
Remember that at the time, Millsap wasn't a good shooter and just a mediocre playmaker. Put the blame on Ty and DL who didn't recognize his full potential and allowed him to fully develop.
Regarding the rebounding, you are looking at it the wrong way.
Total rebounds is a bad indicator (and simplistic one). You need to take into account pace, minutes played, rebounds available, players on the team. For instance, Favors has never averaged as many minutes as Millsap. When Millsap had 8.8 rpg, he also averaged 3 more minutes per game than Favors in his best rebounding season (8.7). And at the same age (27), Millsap had 7.1rpg on 30.4mpg, same as Favors now in only 23mpg. Also, Millsap have played with weaker rebounding centers than Favors (Rudy), which reduces the number of rebounds available. Also, Utah's pace was a bit faster with Sloan than with Ty the Turd and Quin so Paul benefited from playing most of his career under Jerry and of course in fast-pace Atlanta and Denver.
And finally: for his career Millsap has a rebounding rate (rebounds he grabbed that were available) of 14.6%, with his rebounding declining steadily since 2012 (it's been between 12-14%). In contrast, and despite the fact he has played with Rudy, Derrick has averaged a rebounding rate of 16% for his career. This year he is averaging 17.2%, a number Millsap only reached the first year oh his career, when he came into the league as a rebounding machine. Since then it's been a decline. Favors got 17.9% in 2012-2013. To put it in context, that would rank in the top 10 almost any year. You can find all this on basketball-reference.
So yeah, based on facts, Favors is a better rebounder. 
